Sunday, October 2, 2016

Season 9, rapid tournament, rounds 25-31

Table after 31 rounds

The first RR is over and we are at the halfway point. Houdini is in front, increasing the gap after 6 points in the last 7. Stockfish and Komodo are tied in second 2.5 points behind. The three leaders are still uneaten in this tournament. A little behind are Ginkgo, Jonny and Fire, forming a second group of 3. Of the under-3000 engines only Texel's performance remains notable in the top half. Fruit and Laser are doing well in the bottom half.

Draw rate of games within the top 10 engines is 29/45 (64%), much higher than the total draw rate.

The Stockfish - Delphil draw stands out as the most outrageous result of the RR, considering that this is half of Delphil's score in the full RR.

What will happen in the reverse games? My feeling is that Houdini will win this tournament, that it is simply playing better, beating the weaker engines where Stockfish and Komodo sometimes slip. A gap of 2.5 points is quite a lot to close in 31 games, especially if Houdini remains unbeaten.

Games that caught my eye

Round 25:
Jonny - Gull: The game had a RN for Q imbalance, and evals favored Gull. As pieces were exchanged the evals continued to climb, reaching over 1 in a RRN vs QR position. With pawns running out Jonny saw a draw coming. Gull without tablebase support did not see it and thought it was winning, playing a 6-man draw for over 50 moves.

Rybka - Houdini: Houdini sacrificed a bishop to get a strong king side attack that turned into a RR vs Q ending. Houdini's two extra pawns were enough to win.

Komodo - Stockfish: Komodo looked good in the start with evals rising to 0.6 and a great spot for a knight. Stockfish remained calm and the game became static with both engines just shuffling. This didn't improve when the position opened up 50 moves later, only the evals coming slowly down until the draw. Houdini was the real winner of the game, extending its lead.

Ginkgo - Naum: Ginkgo was happy to win a pawn leading to a QB vs QB position, evals climbing above 1. Since the bishops were of opposite color Naum tried to force a queen exchange, and the evals came back down as this was achieved. Then it was just a long wait for adjudication. A missed chance for Ginkgo.

Round 26:
Stockfish - Ginkgo: Nothing in this game, just exchanging pieces and waiting for the draw.

Houdini - Komodo: Houdini had a little more space than Komodo, but Komodo had a strong pawn line that together with a bishop closed all files. Both engines shuffled pieces until draw was declared. Both head-to-head matches of the top engines were draws, Houdini remains 2 points in front.

Andscacs - Jonny: Andscacs exchanged down to a rook ending a pawn up, with evals approaching 1. Jonny then used its tablebase knowledge to reach a drawn 6-man, with Andscacs playing on for 20 moves thinking it has a winning chance. Only Fire improving its score at the top in this round.

Jonny - Chiron: The game started with an unusual imbalance of BN and pawns for Q. Both engines thought they were better, and even though Jonny exchanged a bishop for a rook the RRB for QR ending was a draw.

Protector - Fire: Fire had no problem defending against Protecor but could get no more the a draw out of the game. Fire and Jonny starting to fall back behind the top 3 in the table.

Komodo - Nirvana: Komodo had an eval advantage from the start, by move 25 only RBB vs RBN were left. Nirvana defended well and Komodo could only get an opposite color bishop ending, a sure draw. Komodo is now tied with Stockfish in second.

Ginkgo - Houdini: Ginkgo thought it had a better position for 20 moves with a passer on the king side. Houdini countered on the queen side (where both kings castled), exposing white's king for attack as well as advancing a passer of its own. Houdini's pawn storm in front of the white king was much more threatening than Ginkgo's passers, and was enough to ensure a win for Houdini. Nothing seems to be able to stop Houdini, this was its last serious opponent of the RR. This was only Ginkgo's second loss of the tournament.

Round 28:
Nirvana - Ginkgo: Ginkgo thought it had an advantage with a bishop pair against Nirvana's two knights. Nirvana managed to exchange down to a N vs B ending which resulted in a quick draw. Four straight games without a win for Ginkgo.

Fire - Hannibal: After many exchanges the position was RN vs RN after 26 moves. The game continued until reaching a drawn tablebase position.

Critter - Jonny: Jonny couldn't get past Critter's defense, its initial eval advantage slowly came down to zero as more pieces came off the board. The Fire - Ginkgo - Jonny group has lost touch with the table leaders, a full point behind.

Fizbo - Houdini: Fizbo succeeded where most engines failed, it held Houdini to a draw. Fizbo had a queen side pawn advantage, while Houdini was a pawn up with doubled central passers. Houdini was able to take out the queen side pawns, leaving its king exposed, enough for Fizbo to force a draw.Round 30:
Fire - Komodo: Neither engine could get something going in the game. By move 33 only B vs N were left and evals were at 0 until adjudication.

Round 31:
Ginkgo - Fire: Fire had an advanced passer but could not get it far enough. Ginkgo closed the game with a bishop sacrifice and a forced repetition by Fire to avoid mate. The second engine group is 1.5 points behind.

Fruit - Stockfish: Stockfish managed to get a small eval advantage in the game but there were not enough pieces left on the board in a QB vs QB ending. A surprise draw to close the RR.